Option 1   If the Call back number is the same from which the PIN has been sent then send only PIN number as a text message.

<PIN><send>

Option 2 - If the Call back number is different to the number you wish to receive the call back on:

<PIN> <space> <Call back number><send>

SMS Call Back Number: 00447712625101

The PIN is an 11-digit number.

The System will call you on the Call Back Number and at the voice prompt you will be asked to enter your destination number.

Once you receive the Call Back the format of your call will need to be: 

<Country code> <Area Code without leading 0 > <phone number>